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CITY OF DUBLIN
AGENDA STATEMENT
City Council Meeting Date: April 11, 1994
SUBJECT:
Annual Traffic Safety Report and Downtown Intersection
Monitoring Report
Report by: Public Works Director Lee Thompson
EXHIBITS ATTACHED:
1) / Traffic Safety Report from TJKM
2) /' Downtown Intersection Monitoring Report
3) /' 1993 Traffic Flow Map (Average Daily Traffic)
4) / Level of Service (LOS) Descriptions.
5) ~c~~~..~tion ~ to be displayed at meeting
~ Receive presentation
RECOM:MENDATION:
FINANCIAL STATEMENT:
No new physical improvements are recommended by this report.
The one recommendation for additional monitoring would be paid
from the Engineering Operating Budget.
DESCRIPTION: In 1987, the City Council directed Staff to prepare a Citywide
Traffic Safety Report which would identify locations that experienced a significant number of traffic
accidents and make recommendations for possible means of improving safety at these locations. Since
that time, Staff, through the City's traffic consultant TJKM, has prepared the Annual Traffic Safety
Reports and presented them to the City Council. This traffic safety report is combined with a
"downtown intersection monitoring" report per the Downtown Specific Plan recommendation.
ANNUAL TRAFFIC SAFETY REPORT
Following is a summary of the information contained in TJKM's report.
A total of 244 reported accidents occurred in 1993, 23 of which were injury accidents. There were no
fatal accidents. The total number of accidents in 1993 is somewhat higher than the 1992 total and
about 4 % higher than the average of the three previous years, which was 235 accidents; however, the
number of injury accidents in 1993 was lower than the 3-year average of 35.
The same method was used in compiling this year's report as was used last year. Intersections and
street segments were selected which had incurred more than three accidents and accident rates were
then calculated for these locations. The accident rate is a function of the number of accidents and
number of vehicles traveling the road segment or entering the intersection per day. The resulting
accident rates were compared with the State average, and those locations which exceeded the State
average were analyzed to see if changes could be made to improve the safety of the intersections or
street segments. Table II of TJKM' s report identifies the locations for which calculations were made
and the comparative accident rates.
The philosophy behind using this method of accident rate comparison is that intersections and roadway
segments with high traffic volumes tend to incur more traffic accidents as a matter of course. An
intersection with a moderate number of accidents and high traffic volume would have a comparatively
low accident rate, while an intersection with few accidents but very low traffic volume could have a
comparatively high accident rate. For example, the Dublin Boulevard/Dougherty Road intersection
had 9 accidents in 1993, and 46,250 vehicles per day entering the intersection. The accident rate at
this intersection is lower than the State of California accident rate. However, the Amador Valley
Boulevard/Brighton Drive intersection had only 3 accidents in 1993, with only 13,100 vehicles per
day entering the intersection. The accident rate at this intersection is much higher than the State of
California accident rate. Such an intersection may need more attention than a location with a higher
number of accidents and a high Average Daily Traffic number (ADT), depending on the types of
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ITEM No.8 .2.
.. C I.TY . C L.E R K
FILE"~.
COPIES TO: TJKM
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accidents that occur. The Average Daily Traffic is the average number of vehicles entering an
intersection or street segment during a 24-hour period.
Six intersections and two street segments were found to have accident rates higher than the State
average. Following is a discussion of the conditions and recommendations for these locations.
Accident diagrams are included as a part of TJKM's report.
Sierra Lane Between Dougherty Road and Sierra Court
Two of the four reported accidents involved vehicles backing up on the south side of Sierra Lane, one
striking a parked vehicle and one striking a turning vehicle. One involved a vehicle pulling away
from the curb on the south side of Sierra Lane striking a vehicle exiting a private driveway. The
fourth involved a left-turning vehicle striking a parked DSRSD maintenance vehicle in a coned-off
area in the center of the street. These accidents were all caused by driver error, and there are no
recommendations.
Sierra Court Between Trinity Court and Sierra Lane
Two of the three reported accidents involved southbound vehicles striking northbound left-turning
vehicles. The other accident involved a southbound vehicle striking a vehicle exiting a private
driveway on the west side of the street. These accidents were caused by driver error, and there are no
recommendations.
Amador Valley Boulevard/Briehton Drive Intersection
This "T" intersection currently operates with stop sign control for Brighton Drive. All three reported
accidents were of the right-angle type involving westbound vehicles on Amador Valley Boulevard
striking vehicles crossing Amador Valley Boulevard from southbound Brighton Drive. The cause in
all cases was an improper movement on the part of the southbound vehicle. This intersection recently
underwent a stop sign study, and it was determined that the warrants for all-way stop sign control had
not been met. Staff is pursuing trimming of bushes at the corner. Recommendation: Monitor the
intersection for an additional year to detennine if funher sight distance improvements will be
necessary.
Dublin Boulevard/Village Parkway Intersection
This intersection operates under traffic signal control. Fourteen accidents were reported at this
intersection. Three were rear-end collisions involving southbound right-turning vehicles. Two were
rear-end collisions involving eastbound vehicles. Two involved vehicles or bicyclists running red
lights. Two involved vehicles exiting driveways striking through vehicles. An additional rear-end
collision involved an eastbound left-turning vehicle that had stopped for conflicting traffic. One
involved an illegal backing maneuver, one involved a driver losing control of the vehicle, and one
involved an unsafe lane change.
Rear-end collisions are most prevalent at high-volume signalized intersections such as this. The
accidents involving southbound right-turning vehicles primarily occur because the movement is Yield-
controlled and drivers often must stop after completing a partial turn. The Dublin Boulevard
Widening improvements anticipated to be constructed later in 1994 will eliminate the concrete
channelizing islands and bring the right turn movement under signal control. There are no further
recommendations.
Dougherty Road/Sierra Lane Intersection
This intersection currently operates with stop sign control on the Sierra Lane approaches. The
westbound approach was recently constructed. Of the three reported accidents at this intersection, one
involved a northbound vehicle on Dougherty Road striking a vehicle exiting a driveway, one involved
a bicyclist on the wrong side of the road, and one was a right-angle accident involving an eastbound
left-turning vehicle. No accident pattern is discernible.
A traffic signal is planned for this intersection later in 1994. There are no further recommendations.
San Ramon Road/Silvergate Drive Intersection
This "T" intersection operates under traffic signal control. Two of the four reported accidents were
caused by southbound vehicles running red lights. The other two accidents occurred nearly
simultaneously as a vehicle from the first accident was rear-ended while being moved to the side of
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the road. Both accidents involved southbound vehicles. These accidents were the result of driver
error, and there are no recommendations.
Dublin Boulevard/San Ramon Road Intersection
Seven of the fourteen reported accidents were rear-end collisions. Two were driveway related. Two
were right-angle type accidents. Of the remaining three accidents, one was caused by an unsafe lane
change, one by an inexperienced driver, and one by a driver with medical problem who lost control of
his vehicle. No significant accident pattern is discernible, and there are no recommendations.
Amador Valley Boulevard/San Ramon Road Intersection
Three of the ten reported accidents were right-angle accidents. All three involved vehicles running
red lights. Three of the accidents were rear-end collisions. Two were sideswipes. One involved a
bicyclist, and one involved a vehicle losing control. No pattern is discernible, and there are no
recommendations.
DOWNTOWN INTERSECTION MONITORING REPORT
This program is part of the Downtown Specific Plan adopted in July of 1987. Five intersections have
been monitored annually since 1987. Turning movement counts were taken in January of 1994 during
the p.m. peak hour at the following intersections and with the following results:
Comparison of Total Intersection Peak Hour Tratfic
Volume Growth Rate
1992 1993 Since 1992 Since 1988
. San Ramon/ Amador Valley 3,396 3,486 +2.7% -5.6%
. Dublin Blvd.lRegional 3,353 3,034 -9.5% -7.2%
. San Ramon / Dublin Blvd. 6,560 5,750 -12.3% -2.3%
. Dublin Bl./Village Pkwy. 3,122 2,973 -4.7% -5.6%
. Dublin Bl./Dougherty Rd. 4,082 4,419 +8.3% +14.7%
Two of the five intersections show traffic growth over last year. The remaining intersections show a
decrease in traffic over last year.
Volume-to-capacity (V/C) ratios were calculated at each of the five intersections to determine the
levels of service (LOS) during the p.m. peak hour. TJKM's report includes a table which compares
the past five years. The summary table below compares 1992 with 1993. The vIe ratio at four of
the five intersections increased or decreased consistent with the overall traffic volume changes. At the
Dublin Boulevard/Dougherty Road intersection, significant capacity improvements decreased the
volume-to-capacity ratio even though the overall traffic volume at the intersection increased by 8.3 %.
Intersection Levels of Service (LOS)
(See Exhibit 4 for LOS descriptions)
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San Ramon/ Amador Valley
Dublin Blvd.lRegional
San Ramon Rd.lDublin Blvd.
Dublin Blvd.lVillage Pkwy.
Dublin Blvd.lDougherty Rd.
1992
vie Ratio LOS
0.66 B
0.73 C
0.92 E
0.71 C
0.79 C
1993
V /C Ratio LOS
0.68 B
0.67 B
0.86 D
0.67 B
0.77 C
The measured volume decreases on Dublin Boulevard may be attributable in part to the recent
construction of shopping centers in Livermore. The measured increase at the Dougherty Road/Dublin
Boulevard intersection is most likely due to the eastern extension of Dublin Boulevard. The small
increase at the San Ramon Road/ Amador Valley intersection is most likely a normal statistical
fluctuation.
All five intersections studied are currently operating at acceptable levels of service based on the City's
standard of acceptability. Therefore, no immediate level of service improvements are recommended
at any of the intersections. a:(9394) Imarch lagsr.sfty
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FINAL REPORT
1993 Traffic Safety Study
In the City of Dublin
March 21, 1994
Prepared by
T JKM Transportation Consultants
4637 Chabot Drive, Suite 214
Pleasanton, California 94588-2754
(510) 463-0611
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93Safely.1K2
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TABLE OF CONTENTS
Page
IN1'R.ODUCTION ...................................... . . . . . . . . . . . .. 1
Accident Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
Method for Selecting High Accident Locations ..................... \ . . . . .. 1
1993 High Accident Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2
RECOMMENDA nONS .............................................. 5
Roadway Traffic Safety Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5
Sierra Lane between Dougherty Road and Sierra Court . . . . . . . . . . . . . . . . . . .. 5
Sierra Court between Trinity Court and Sierra Lane .. . . . . . . . . . . . . . . . . . . .. 7
Intersection Traffic Safety Improvements ................................ 9
Amador Valley Boulevard and Brighton Drive. . . . . . . . . . . . . . . . . . . . . . . . .. 9
Dublin Boulevard and Village Parkway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11
Dougherty Road and Sierra Lane ................................... 13
San Ramon Road and Silvergate Drive ............................... 15
Dublin Boulevard and San Ramon Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17
Amador Valley Boulevard and San Ramon Road. . . . . . . . . . . . . . . . . . . . . . .. 19
TABLES
I Traffic Accidents By Year .......................................... 1
II Summary of 1993 Accidents For Roadway Segments and Intersections ........... 3
III Comparison of 1992 and 1993 Accident Ratios . . . . . . . . . . . . . . . . . . . . . . . . . .. 4
COLLISION DIAGRAMS
1 Sierra Court between Trinity Court and Sierra Lane (Collision Diagram 1) . . . . . . .. 6
2 Sierra Lane between Dougherty Road and Sierra Court (Collision Diagram 2) ..... 8
3 Amador Valley Boulevard and Brighton Drive (Collision Diagram 3) ........... 10
4 Dublin Boulevard and Village Parkway (Collision Diagram 4) ................ 12
5 Dougherty Road and Sierra Lane (Collision Diagram 5) . . . . . . . . . . . . . . . . . . . .. 14
6 San Ramon Road and Silvergate Drive (Collision Diagram 6) . . . . . . . . . . . . . . . .. 16
7 Dublin Boulevard and San Ramon Road (Collision Diagram 7) . . . . . . . . . . . . . . .. 18
8 Amador Valley Boulevard and San Ramon Road (Collision Diagram 8) . . . . . . . . .. 20
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INTRODUCTION
'.
Each year the list of reported accidents within the City is reviewed to determine if there are serious traffic
safety problems that can be corrected. The following study report provides a description of the overall
accident trends in the City. identifies locations where traffic safety is below average. and makes
recommendations to revise traffic control to enhance vehicle safety. In summary. the 1993 traffic safety
analysis has found that:
. The total number of reported accidents has increased slightly over 1992 levels. and has
increased four percent over the previous three-year average.
. Two roadway segments and six intersections were found to have accident rates that are
higher than the State average for these types of facilities.
. One location is in need of traffic control improvements. All other high accident rate
locations were found to have current and standard traffic control measures. or are currently
being improved.
Accident Trends
The 1993 reported accidents were totalled by severity and compared to the previous accidents for 1990
through 1992. The resulting accident trends are listed in Table I.
Both property damage and injury accidents have slightly increased over last year. Similarly, the total
number of accidents increased 4 percent compared to the previous three-year average. Property damage-
only accidents are 11 percent higher than the three-year average. but recorded injury accidents decreased
by 34 percent over the average. (Changes in definition and recording of injury accidents may have
contributed to the apparent decrease.) There were no fatal accidents.
Table I
Traffic Accidents By Year
Number of Accidents Three- 1993
Year
Accident Type Average % Change
19'Xl 1991 1992 Total
Property Damage Only 179 2m 214 200 221 +11%
Injury 72 16 18 35 23 .34%
Fatal 0 0 0 0 0 N/A
Total Accidents 251 223 232 235 244 +4%
Method for Selecting High Accident Locations
High accident locations were selected by reviewing the 1993 Accident Spot Map, and calculating the
accident rate for road segments or intersections. The map is a graphic record of the collision reports
prepared by the City of Dublin. The accident rates were then compared to State average accident rates
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 1
March 21,1994
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according to the type of roadway or intersection. Any locations that were found to have a higher rate
(worse than statewide average accident rate) was noted for further study.
The accident rates for roadway segments between intersections were calculated by Equation 1.
roadway daily volumes were taken from the 1993 Traffic
Flow Map prepared by TJKM for the City. The length of
a roadway segment was interpreted to be the distance (in
miles) between adjoining intersections. Typically. roadway
segment calculations are more appropriate for rural settings
(~". J) RD<JJw., Se,_'" R....
where there are longer distances between major
intersections. When applied to short segments. the resulting
accident rates can be artificially high compared to State averages.
The
AccidentRaU = Accidentsxl,OOO,OOO
ADTxMUux36S
For intersections. the accident rates were calculated by Equation 2. The intersection daily volumes were
taken as the sum of each approach to the intersection. The
accident rates were compared by facility type with the
standard rates published in Caltrans' 1991 Accident Data on
California State Highways. In order to select study
locations for the traffic safety study. the ratio of the
(Eq", 2) J"'euectiOll R,.e
calculated rate was taken for a given location to the
Caltrans rate for similar facilities.
AccidentRate= Accidmtsxl,OOO,OOO
ADTx36S
1993 High Accident Locations
Table II indicates the eight high accident locations (six were intersections. two were roadway segments)
in 1993 ranked by the ratio described above. Other locations that had three or more reported accidents.
but lower than average accident rates are also listed. Collision diagrams. included in Appendix A. were
prepared for the high accident locations.
Table III contains a comparison of 1993 accident rates with those of 1992. As the table indicates. only
one road segment with an accident ratio greater than one in 1992 retained a ratio greater than one in 1993.
No study intersections with 1992 ratios greater than one retained ratios greater than one in 1993. Some
of the improved rates are likely due to recent safety improvements. and some are attributable to standard
yearly fluctuations.
1993 Traffic Safety Study
T JKM Transportation Consultants
Page 2
March 21,1994
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Table n
Length State
Location Accidents ADT (t'L) Rate" Rate~ Ratio.
Road SegmentSS
Sierra Ln.. Sierra Cl to Dougherty Rd. 4 4.700 1.400 8.80 3.70 """"'""..238<
.... .... ..
.... ..... ..
... .. .
Sierra Ct. Sierra Ln. to Trinity Cl 3 3.750 1.450 8.00 3.70 i.2J6
... ... ..
... .,. . ...
. . . . . . . . . . .
"'Villi'g~'pj(;y::"jj~bllii"B'i~;~CU;'A~d~"V8li~y'Bi"~d:;'''''''' ......................... .................... . . . , . . . .
...........i~65o.. .......4:3"8".. .......450.... ..................~
8 16.000 0.98
Amador Valley Blvd.. StarWard Dr. to Regional St" 4 20.350 800 3.55 4.50 0.79
Dublin Blvd.. Regional St. to Golden Gate Blvd." 6 21.800 1,250 3.19 4.50 0.71
San Ramon Rd.. Dublin Blvd. to Amador Valley Blvd." 3 24.350 1.200 1.49 3.50 0.42
Dublin Blvd.. Clark Ave. to Sierra Ct." 3 22,750 1,100 1.73 4.50 0.39
Dublin Blvd.. Regional St. to San Ramon Rd." 4 28.300 600 3.41 4.50 0.76
Intersections
Amador Valley Blvd./Brighton Dr. 3 13.100 0.63 0.17 /3.71,.
Dublin Blvd.Nillage Pkwy. 13 31,300 1.14 0,54 / 2;11
Dougherty Rd./Sierra Ln. 9 25.700 0.32 0.17 1.88
San Ramon Rd./Silvergate Dr. 5 26.800 0,51 0.34 LSO
Dublin Blvd./San Ramon Rd. 14 56.400 0.68 0.54 1.26
Amador Valley Blvd.ISan Ramon Rd. 10 44,100 0.62 0.54 <<,,",'1.15'
. ..... ..
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...i':iC;~ghertY.Rd:ii':i~bfui.Biv.d:<"................ .................................... ............9........... .....46;15'0.. .......0:53.... .......0:54.... .........0:98..'
Dougherty Rd,fAmador Valley Blvd." 4 24.800 0.44 0.45 0.98
San Ramon Rd.Nomac Dr." 4 21.000 0.52 0.54 0.96
Dublin Blvd./Dublin Ct." 3 25.900 0.32 0.34 0.94
Dublin Blvd./Golden Gate Dr." 5 27,050 0.51 0.54 0.94
Dublin Blvd./Regional St." 5 32.400 0.42 0.54 0.78
San Ramon Rd.IShannon Ave." 3 21.250 0.39 0.54 0.72
Amador Plaza/Dublin Blvd." 3 26.100 0.31 0.54 0.57
a. The accident rate is measured in accidents per million vehicles for intersections and per million vehicle-miles for roadway
segments.
b. Accident rates are categorized on the basis of facility size, configuration, type of control and area density. All
intersections are in the "Suburban" category.
c. Ratio = Calculated Rate/Caltrans Rate
d. Road segment rateS calculated for length of roadway between adjacent intersections.
e. Three or more accidents occurred at this facility in 1993, but the facility's accident rate was below the statewide average.
Summary of 1993 Accidents
For Roadway Segments and Intersections
1993 Traffic Safety Study
T JKM Transportation Consultants
Page 3
March 21. 1994
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Table ill
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Comparison of 1992 and 1993 Accident Ratios
1993
1992
Location
Accidents
Ratio'
Accidents
Ratio'
Road Segments
Sierra Ln., Sierra Cl to Dougherty Rd. 4. ....>:p~ 3 .H<: 1~84
Sierra Ct, Sierra Ln. to Trinity Ct. 3 ........./2~16 . -
..............................................................................................,........ ........................... ........;;..;.............; ........................... ..........................
Village Pkwy., Dublin B1. to Amador Valley BI. 8 0.98 . .
Amador Valley B1.. Starward Dr. to Regional St: 4 0.79 . -
Dublin B1., Regional St to Golden Gate B1.' 6 0.71 - -
San Ramon Rd.. Dublin B1. to Amador Valley B1.' 3 0.42 - -
Dublin B1., Clark Ave. to Sierra Ct.' 3 0.39
Dublin 81., Regional St. to San Ramon Rd.' 4 0.76
Dougherty Rd., Houston PI. to Sierra Ln. - -
Village Pkwy., Lewis Ave. to Dublin BI. . -
Dublin BI., Dublin Ct to Civic Plaza" - -
3 .:::.-- '.:.::::::::>.:r"SO:.:.'
4 .< <1:oiH
3 0.53
Intersections
Amador Valley BI./Brighton Dr. 33.71'-
Dublin B1.Nillage Pkwy: 132.11 8 0.97
Dougherty Rd./Sierra Ln. 9 1.88 - -
~:b~~~.;S:.:::g~:.~. :4i"ii~ 1 ~ 0.7~
Amador Valley BI./San Ramon Rd: 10 :'. :.. ........1.15 9 0.96
...~:::::.~:.:~~~~B~:~~;..~~~~.................................. .............~. ........... ;........;.......~:::.: ....................T:.. r:uu::i::i:i!~'i~>
San Ramon Rd.Nomac Dr.' 4 0.96 . -
Dublin BI./Dublin Ct' 3 0.94 - -
Dublin BI./Golden Gate Dr.' 5 0.94 8>1.15
Dublin B1./Regional St.' 5 0.78 121.39
San Ramon Rd./Shannon Ave.' 3 0.72 . -
Amador Plaza/Dublin BI.'" 3 0.57 6 0.83
Dougherty Rd./I-580 WB Off-Ramps4 - - 13 . "H" H 238 .
Amador Valley B1./Regional Sl - - 3 ".u"l:06-
Amador Valley BI.Nillage Pkwy: . - 6 0.71
Dublin BI./Sierra Ct./Civic Plaza" - - 4 0.61
a. Ratio '" Calculated Accident RatelCaltrans Accident Rate
b. Three or more accidents occurred at this facility in 1993, but the facility's accident rate was below the
statewide average.
c. Three or more accidents occurred at this facility in 1992, but the facility's accident rate was below the
statewide average.
d. This intersection is located inside City limits but falls under Caltrans' jurisdiction
1993 Traffic Safety Study
TJKM Transportation Consuffants
Page 4
March 21, 1994
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RECOMMENDATIONS
.
Roadway Traffic Safety Improvements
1. Sierra Lane between Dougherty Road and Sierra Court (Collision Diagram 1)
Two of the four reported accidents involved vehicles backing up on the south side of
Sierra Lane, one striking a parked vehicle and one striking a turning vehicle. One.'
involved a vehicle pulling away from the curb on the south side of Sierra Lane
striking a vehicle exiting a private driveway, The fourth involved a leftwturning
vehicle striking a parked City maintenance vehicle in a coned-off area in the center
of the street,
Recommendations: None
1993 Traffic Safety Study
T JKM Transportation Consultants
Page 5
March 21, 1994
ACC DATE TIME
1 02~ 10-93
2 03~02-93
3 03-26~93
4 06-11-93
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LEGEND:
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Right Angle
Left Turn
Rear-End
Head-On
Side Swipe. Rear-End
Side Swipe, H,ea~-On
Pedestrian. Bicycle
Backing
Daylight
Darkness
Property Damage
Fixed Object
Injury
Fatal
Parked Car
Out of Control
CITY OF DUBLIN
LOCATION:
Sierra Lane between
Dougherty Road and Sierra Court
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
Sierra Court
Collision Diagram [JJ
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North
157.oo1T8 - 2/94 - K2
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2. Sierra Court between Trinity Court and Sierra Lane (Collision Diagram 2)
Two of the three reported accidents involved southbound vehicles striking
northbound left.tuming vehicles. The other accident involved a southbound vehicle
striking a vehicle exiting a private driveway on the west side of the street,
..,....., ." , .. ., _~.', ". ,.' .,._ _,.". . .". .... .. ,,' .'~U .',' ..._,."
Recommendations: None
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 7
March 21 t 1994
ACC
DATE
1
2
3
05-25-93
07-21-93
09-09-93
TIME
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Collision Diagram [I]
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LEGEND:
~ Right Angle
~ Left Turn
-----0-- Rear-End
-0- Head-On
: () Side Swipe. Rear-End
- ,. 4 () . "Side Swipe-; Head~On
~KE Pedestrian. Bicycle
~ Backing
(L) Daylight
(0) Darkness
o Property Damage
o Fixed Object
o Injury
. Fatal
D> Parked Car
MA-.. Out of Control
CITY OF DUBLIN
LOCATION:
Sierra Court between
Trinity Court and Sierra Lane
PERIOD COVERED:
01.01.93 to 12.13.93
DATE COMPILED: 02-09-94
~
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North
157-OO1T8 - 2194 - K2
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Intersection Traffic Safety Improvements
1. Amador Valley Boulevard and Brighton Drive (Collision Diagram 3)
This three.legged intersection currently operates with STOP sign control on the
southbound approach., All three of the .reportedaccidents were ,of the right~angle .
type involving westbound vehicles on Amador Valley Boulevard striking vehicles
crossing Amador Valley Boulevard from southbound Brighton Drive (in one case, a
bicycle was the southbound vehicle). The cause in all cases was improper movement
on the part of the southbound vehicle. TJKM recently determined that all-way STOP
control is not warranted at this intersection.
Recommendations: Monitor the intersection for an additional year to determine
if sight distance improvements will be necessary,
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 9
March 21. 1994
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DATE
TIME
1
2
3
08~ 10-93
08-28-93
10-04-93
09:00
17:49 L
14:45 L
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Right Angle
Left Turn
Rear-End
Head-On
Side Swipe, Rear-End
Si~~ S.vipe, Head~O~_
Pedestrian, Bicycle
Backing
Daylight
Darkness
Property Damage
Fixed Object
Injury
Fatal
Parked Car
Out of Control
Amador valley Blvd,
Collision Diagram m
CITY OF DUBLIN
LOCATION:
Amador Valley and
Brighton Street
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
..
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North
157,(l()1TS - 2/94 - K2
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2. Dublin Boulevard and Village Parkway (Collision Diagram 4)
This intersection operates under traffic signal control. Fourteen accidents were
reported at this intersection. Three were rear-end collisions involving southbound
right.turning vehicles. Two were rear-end collisions involving eastbound vehicles.
Two involved vehicles or bicyclists running red lights. .Two involved vehicles exiting.
driveways striking through vehicles (one vehicle illegally exited the Wendy's
driveway), An additional rear end collision involved an eastbound left-turning
vehicle that had stopped for conflicting traffic. One involved an illegal backing
maneuver, one involved a driver losing control ofthe vehicle, one involved an unsafe
lane change,
Rear-end collisions are usually most prevalent at high-volume signalized
intersections such as this. This type of accident accounts for 46 percent of the
accidents at this intersection. The accidents involving southbound right-turning
vemcles primarily occur because the movement is YIELD-controlled and drivers often
must stop after completing a partial turn. In conjunction with the planned widening
of Dublin Boulevard, the City plans to eliminate both right turn channelizing islands
on Village Parkway which will bring both the southbound and westbound right-turn
movements under signal controls,
Recommendations: Pursue the planned widening of Dublin Boulevard including
removal of the right turn channelizing islands on the north leg of Village Parkway.
1993 Traffic Safety Study
T JKM Transportation Consultants
Page 11
March 21, 1994
ACC DATE TIME
1 01-2893 0840 L
2 01-29-93 15:47 L
3 05-17-93 13:15 L
4 05-21-93 10:00 L
5 06-19-93 18:15 L
6 06-27-93 17:49 L
7 07-23-93 17:20 L
8 08-13-93 15:20 L
9 09.-10-93 - 15:10 L
10 10-26-93 17:15 L
11 11 ~09-93 14:25 L
12 12-02-93 10:45 (L)
13 12-02-93 17:30 D)
e
fll
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Collision Diagram m
~'i~" ..
". .-:-:.... ... ,......
.". ...... .:"-: '
e
LEGEND:
~
-0-
-0-
~ ()
~ () .
....~IKE
~
(L)
(0)
o
o
e
.
[J>
-1NI-..
Right Angle
Left Turn
Rear-End
Head-On
Side Swipe, Rear-End
Side Swipe,. H~ad.-On
Pedestrian, Bicycle
Backing
Daylight
Darkness
Property Damage
Fixed Object
Injury
Fatal
Parked Car
Out of Control
Dublin Blvd.
CITY OF DUBLIN
LOCATION:
Dublin Blvd. and
Village Parkway
PERIOD COVERED:
01-01-93 to 12-13.93
DATE COMPILED: 02.09-94
~
~
North
15HlO1T8 - 2194. K2
e
e
3. Dougherty Road and Sierra Lane (Collision Diagram 5)
This intersection currently operates with STOP sign control on the Sierra Lane
approaches (the westbound approach was recently constructed). Of the three
accidents reported at the intersection, one involved a northbound vehicle on
Dougherty Road striking a vehicle exiting a driveway, one involved a bicyclist on the
wrong side of the road, and one was a right-angle accident involving an eastbound
left-turning vehicle and a southbound vehicle, No accident pattern was discernible
at the intersection.
A traffic signal is planned for the intersection in the near future. No additional
measures are recommended.
Recommendations: Pursue the planned installation of a traffic signal at the
intersection.
1993 Traffic Safety Study
T JKM Transportation Consultants
Page 13
March 21, 1994
I
I
I
I
I
/
/
- - - ..... .... - -... - --~ ..... .; /
e
ACC
DATE
TIME
1
2
3
06-08-93
10-01-93
12-13-93
! ~".'.'
y
Sierra Lane
2
=11UIKE
'0
~
o
0:
>-
t:
Cl.l
.r:
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Collision Diagram []]
e
LEGEND:
1:=
--0-
-0-
:0
40
'~BI;E
~
(L)
(D)
o
o
19
.
D>
'2N\-o..
Right Angle
Left Turn
Rear-End
Head-On
Side Swipe, Rear-End
Side S\y,ipe, Head-On
Pedestrian, Bicycle
Backing
Daylight
Darkness
Property Damage
Fixed Object
Injury
Fatal
Parked Car
Out of Control
....
"
..:..:...:....,
..... \
\
\
CITY OF DUBLIN
LOCATION:
Dougherty Road and
Sierra Lane
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
II
North
~
157-OO1T8 .V!:l4. K2
e
e
4. San Ranwn Road and Silvergate Drive (Collision Diagram 6)
This three-legged intersection operates under traffic signal control. Two of the four
reported accidents were caused by southbound vehicles running red lights, The other
two accidents occurred nearly simultaneously as a vehicle from the first accident was
rear-ended while, being moved, to the" side of the road (both accidents ,involved "
southbound vehicles).
Recommendations: None
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 15
March 21, 1994
e
ACC
TIME
DATE
1
2
3
4
Silvergate Drive
"C
(Q
o
a:
c
o
E
Cl3
c::
c
(Q
CJ)
Collision Diagram ~
,> "',."'.. ,.. ,.
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be'
21
,
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, "
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3 I
---"..0
LEGEND:
j:=
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-0-
:()
I () .
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~
(L)
(0)
o
o
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.
0>
-o/lI4.
Right Angle
Left Turn
Rear-End
Head-On
Side Swipe, Rear-End
,Si..~~~~ipe," .':"l~f'1d~~!1
Pedestrian, Bicycle
Backing
Daylight
Darkness
Property Damage
Fixed Object
Injury
Fatal
Parked Car
Out of Control
CITY OF DUBLIN
LOCATION:
San Ramon Rd. and
Silvergate Drive
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
..
~
North
15HlO1T8 - 2/94 - K2
e
e
5. Dublin Boulevard and San Ramon Road (Collision Diagram 7)
Seven of the fourteen reported accidents were rear-end collisions. Two were
driveway-related. Two were right-angle type accidents. Of the remaining three
accidents, one was caused by an unsafe lane change, one by an inexperienced driver
(who struck-a pedestrian on the sidewalk), and one, by an alcohol-iniluenceddriver
who lost control of his vehicle. No significant accident pattern was discernible at the
intersection.
Recommendations: None
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 17
March 21. 1994
ACC
DATE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
01-13-93
01-23-93
01-25-93
01-26-93
04-04-93
06-08-93
06-18-93
08-19-93
09-22-93
09-25-93
10-06-93
10-22-93
11-23-93
12-30-93
st
",....,""""',..~
. ...... ...
......... ...
.. ... ....
... .".. ..
,,', '.',",'.y 11' 00 .:..:.: " ", ,'..
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TIME
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Collision Diagram [1]
LEGEND:
0- Right Angle
-if Left Turn
-0- Rear-End
-0- Head-On
: () Side Swipe, Rear-End
.. () I Side Swipe, Head-On
~BIKE . Pedestrian, Bicycle
~ Backing
(L) Daylight
(0) Darkness
o Property Damage
o Fixed Object
@ Injury
. Fatal
0> Parked Car
~ Out of Control
.. . . ......
. . ......
... ,...
, "..
... ......
....... ........
...... 2' ,".., "
,,~<""'.',;"..'"
CITY OF DUBLIN
LOCATION:
Dublin Blvd, and
San Ramon Rd.
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
g
~
North
'57.00 1TO .21114 . K2
6.
Amador Valley B!tevard and San Ramon Road (COllis. Diagram 8)
Three of the ten reported accidents were right-angle accidents. All three involved
vehicles running red lights. Three of the accidents were rear-end collisions, Two
were sideswipes. One involved a bicyclist, and one involved a vehicle losing control.
No pattern was discernible at the intersection.
Recommendations: None
. ._..._......_.....J-r..'...a.n'..:... .._~'~ .......,._..."'....~..~rJ.~.. ..._...~'..~_,..'~.:..~.__.. r_..~..._~,,,'"lr. ~.~'.'..., ,<' .,.....,,~......'
1993 Traffic Safety Study
TJKM Transportation Consultants
Page 19
March 21, 1994
e
e
ACC DATE TIME LEGEND:
1 02-05-93 S- Right Angle
2 02.27-93
3 03.18-93 Left Turn
4 03-25-93 -0- Rear.End
5 04-27-93
6 06-14-93 --0- Head-On
7 08-23.93 :() Side Swipe, Rear-End
8 09-29.93 . () I "Sieje Swipe" ,fjead~qn .,
9 11-07-93 ,.". - -, . ~ .' ., .."' ~ ,
10 12-09-93 ~B1Ke Pedestrian, Bicycle
-()<<+<- Backing
(L) Daylight
(0) Darkness
0 Property Damage
0 Fixed Object
@ Injury
. Fatal
0> Parked Car
'V\I4 Out of Control
'0
a:
c::
o
E
C';l
a:
c
C';l
en
Collision Diagram [[]
CITY OF DUBLIN
LOCATION:
Amador Valley and
San Ramon Rd.
PERIOD COVERED:
01-01-93 to 12-13-93
DATE COMPILED: 02-09-94
~
~
North
157.oo1T8.2194 - K2
~ Tro___n eonou....
MEMO
e
March 23, 1994
Project No.: 157"'()()1 Task 9
From:
Mr., Mehran Sepehri, . "... ._." "'._
Carl D. Springer and Christopher S. Kinzel uW
To:
Subject:
Downtown Dublin Traffic Monitoring
Background
The traffic counts for the annual Downtown Dublin traffic monitoring program have been
completed. The program is part of the Downtown Specific Plan adopted in July 1987. the
monitoring program consists of traffic counts taken annually at key intersections within and
leading to the Downtown area.
Five intersections have been monitored annually since 1987, Turning movement counts were
conducted in January 1994 (used for 1993 analysis), during the p.m. peak hour at the
following intersections:
. San Ramon Road/Amador Valley Boulevard
. Dublin BOulevard/Regional Street
· San Ramon Road/Dublin Boulevard
· Dublin Boulevard/Village Parkway
. Dublin Boulevard!Dougherty Road
San Ramon Road and Dougherty Road are major commuter routes providing important north.
south mobility between San Ramon and Pleasanton. These roads provide access to the heart
of Dublin via Dublin Boulevard and Amador Valley Boulevard.
The intersections of San Ramon Road/DUblin Boulevard and Dougherty Road/DUblin
Boulevard serve as gateways to the City, but their operation is very much affected by through
traffic with origins and destinations outside of Dublin,
Analysis
Table I indicates the total volume entering each intersection from 1988 through 1993. For
each intersection, the annual growth rate was calculated between 1992 and 1993 as well as
from 1988 to 1993.
4637 Chabot Drive, Suite 214, P1easanton, CA 94588-2754, (5
P.....nton , SlIer.mlnto . Fl'1lsno . Santa Rosa
...- --, I') _
.....,... .,".:J ~ , .,J ~
l~'HtnU~-~
Mr, Mehran Sepehri
e
Page 2
e
March 23. 1994
Table I
Annual Growth
Rate (percent)
- ~ ". . - ~.." ,. - ". ~. . "on'~"'" '.....,:.., " "r.' _ ,'"." " "',~' '. ..~ 1'-- -,
Since Since
Intersection 1988 1989 1990 1991 1992 1993 1992 1988
San Ramon Rd.! 3.692 3,389 3.320 3,300 3.396 3,486 +2.7% -5.6%
Amador Valley Blvd.
Dublin Blvd.! 3,271 3,285 3,630 2.995 3.353 3,034 -9.5% .7.2%
Regional St
San Ramon Rd.{ 5,884 5.945 5,465 5.890 6.560 5,750 -12.3% -2.3%
Dublin Blvd.
Dublin Blvd.! 3,148 3,259 2,926 2,757 3,122 2,973 4.7% -5.6%
Village Pkwy.
Dublin B1vd.1 3,853 4,054 4,360 4,475 4,082 4.419 +8,3% + 14.7%
Dougherty Rd.
TOTAL 19,848 19,932 19,701 19,417 20,513 19,662 -4.1% .1.1%
Comparison of Total Intersection Peak Hour Traffic
Two of the five intersections studied show traffic growth over last year: San Ramon
Road/Amador Valley Boulevard and Dublin Boulevard/DOugherty Road. The remaining
intersections show a decrease in traffic over last year.
Volume-to-capacity (VIe) ratios were calculated for each of the five intersections to determine
the levels of service (LOS) during the p.m. peak hour. Table II shows a comparison of the
levels of service for 1989. 1990. 1991. 1992 and 1993. (Detailed calculations are attached.)
As the table indicates, for four of the five intersections studied. the V Ie ratio increased or
decreased with the overall volume (as would be expected). At the intersection of Dougherty
Road and Dublin Boulevard, however, significant improvements to the capacity of the
westbound approach resulted in a decreased VIC ratio even though the overall traffic volume
at the intersection increased by 8.3 percent.
Mr. Mehran Sepehrl
e
Page 3
e
March 23. 1994
Table IT
1989 1990 1991 1992 1993
. '.~. ,.Intersection '"." ,"'".' y'!c;... }".O~", .. , :V/c;.",,~9~_ ".. ..V!f ,)~<:>~. ,-'." . .Y!f ."".~Q~, '. Y!~, ...~Q~, ,.-
San Ramon Rd.1 0.71 C 0.66 B 0.65 B 0.66 B 0.68 B
Amador Valley Blvd.
Dublin Blvd./ 0.75 C 0.85 D 0.65 B 0.73 C 0.67 B
Regional Sl
San Ramon Rd.1 0.96 E 0.89 D 0.89 D 0.92 E 0.86 D
Dublin Blvd.
Dublin Blvd./ 0.74 C 0.67 B 0.62 B 0.71 C 0.67 B
Village Plcwy.
Dublin Blvd./ 0.80 C 0.85 D 0.87 D 0.79 C 0.77 C
Dougherty Rd.
Intersection Levels of Service
Notes: V /C := V olume-to-Capacity Ratio
LOS := Level of Service
Conclusions
The measured volume decreases on Dublin Boulevard may be attributable in part to the recent
construction of alternative shopping centers in Livermore (Le. Wal-Mart. Target, Mervyns),
resulting in a shift in travel patterns from the Dublin downtown area. The measured increase
at the Dougherty Road/Dublin Boulevard intersection is most likely due to the recent Dublin
Boulevard eastward extension. In fact, the traffic on the east leg of Dublin Boulevard
increased by a factor of 1.7 (during the p.m. peak hour) over 1992. while traffic on most of
the remaining intersection movements decreased. The measured increase at the intersection of
San Ramon Road and Amador Valley Boulevard (2.7 percent) is small enough to be
attributable to expected statistical fluctuations.
All five intersections studied are currently operating at acceptable levels of service based on
the City of Dublin's LOS standard of acceptability. Therefore, no level of service
improvements are recommended for any of the study intersections.
pJp
Mwhmml
157.oou.u.K2
7,000 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - '
6,500 - - - - - + - - - - - - - - - - - - - - - - -
, "' ,. _. ....,."... ' ., ~ ',.. . '_.' '.. " ~.~ . ~. ~'.. .,.~.... . ."". _~.' _'" ,....d. ," '.. ... ." J. "-^', " ..,_.... ...~.......~ ~...... _. ~.,.... .. y....... '...... '......~,~.........~I.."...' .........~"O't'> 1"___........M... ,,~.. ....... .........., .~.-,....""_..... 'r'" .~....,.,.... ~ -!- "......~... -.'~ _.~ w, 'I-". ~.
6,000
5,500 - - - - - - + - - - -
--+---~----~_....-----
-
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':' 5,000 - - - - - - +- - - - - - ~ - - - - - ~ - - - - -- - - - - - - .
='
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"0 4,500
:c
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>
4,000
3,500
3,000
2,500
1988
- ~ - - ~ - - - - -~ ---~------------- ---
,
,
- - -,- - - - - -
,
1989
1990
1991
1992
1993
Year
City of Dublin
1993 Traffic Monitoring Study
Peak Hour Intersection Volume Trends
157.CX)1.T9- 2/94. K2
. ... . San Ramon/Amador Valley
---tr- Dublin/Regional
-x- San Ramon/Dublin
. DublinNillage
----0-- DublilLDougherly
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Level of lCU
service Traffic Flew QJ.ali ty Value
A I.cM volt.JmeS; high soeeds ( sP?Erl not restricted o to 60%
by othf?r vehicles; all s~gpa.l cycles clear with
no vehicles wai ti.n3' 'thrt:lugl1mre than one
signal cycle.- . ... " .~ '-c." .. .- , ,'"' . ~ ", ',' ... ~ " . . ~. .., "
E a::eratin; sceEds l:eginning to be affected. by 61 to 70%
ot.'1er traffic; between one arrl ten ~~t of
t.'1e si~ cycles r.ave one or more vehicles
whic;:h wait tlirouah mre than one signal cycle I
durm;r peak traffic perio:is.
c a::eratj,w soeeds ani maneuverability closely 71 to 80%
cOntrolled by other traffic; between 11 an:!
30 perq=I;lt 01: the signal = have one or
more vehicles which wait gh more than one
signal cycle durj.n; pe?k traff~c periOOs;
recammen:led ideal rural design star:dard.
D Tolerabl~ ooeratittJ ~; 31 to 70 pep;::e{lt 81 to 90%
of the s~~ cycle have one or lIOre vehicles
which wai throUah mre than one si~ cycle
dur:j..m reak traf~ic ~icrls; often Use:i as
des~gn starrlard ll1 uii:::an areas.
E Caoacity; the:max:inl11m traffic volume an inter- 91 to 100%
seCtion can ao:::anrrcdate; I'l?Stricted ~;
71 to 100 ~t of the s~~ = have
one or :rro~ vehicles which wait ah nore
t.ha1:1 one s~gnal cycle ch.1r~ peak traffic
per~o:1s .
F r..om queues of traffic; unstable flCM; stoP- Not
~es of ~ duration; traffic volume ani" }I'.e.aningful
ffic can ~ zero; traffic
volume w' 1 l:::e less the volume which
cccurs at level of service E.
lEVEL OF SERVICE DESauPrIONS
AT INTERSECTIONS
(a) Although t.'1e Hiahwav ca:cacit-l ?I.arrual reo:::rmnerrls the al::cve
relationship l:ei:Ween LeVel or serv~ce an:l volume to camci ty
ratios, field observation shews that a mre appropriate .
relationshio is as follC1.V'S: .
A, 0 to 6b%; B, 61 to 70%; C6 71 to 80%;
D, 81 to 90'S; am E, 90 to 10 %
Source: Hiahwav Caoacitv Manual, Hiahway Resea-'l'"'C.i. Eoard
Soec~al Recore 87i Nat:.:.cnll JAca:aemy of Sciences,
Wash..i..n:Jton- D.C., 965, Page 320.
~~'~'~~CLDst~~\
e
.
Descriptions of Conditions for Various Levels of Service
FOR STREET SEGMENTS
Level of Service
Operating Conditions
A
Free flow; speed controlled by driver's
desires. speed limits. or physical roadway
conditions.
:,' ,"'.' ,~.. ......., ~,...". -'" "_ .._.. ,p.r _. .. _._ ,~~ '" "H,P ---. ~~- ~-'-'~"~'~
.. _u . ..... .' .. _. ...... ',,'.. ,""~".' .....".
B
Stab Ie flows; operating speeds beginning
to be restricted; little or no restrictions
on maneuverability from other vehicles.
C
Stable flow; speeds and maneuver9Rility
more closely restricted.
o
Approaches unstable flow; tolerable speeds
can be maintained. but temporary
restrictions to flow cause substantial drops
in speed. little freedom to maneuver t
comfort and convenience low.
E
Volumes near capacity; flow unstable;
stoppages of momentary duration. Ability
to maneuver severely limited.
F
Forced flow; low operating speeds; volumes
below capacity t queues form.